Patent GB-774457-A (GB)
Title: Synthetic ester lubricant blends
Filed: 1955-06-03
Abstract: The ingredients of a lubricating composition (see Group III) include a C6-C16 branched-chain alcohol diester of a dicarboxylic acid, a complex ester and phenothiazine.  The blend of diester and complex ester may be prepared by refluxing a mixture of 2 mols. of azelaic acid, 1 mol. of a polyethylene glycol having a molecular weight of about 200 and 2.4 mols. of a C8 oxo alcohol, in the presence of toluene and sodium bisulphate, until no further formation of water occurs.  The crude product may be washed, first with caustic soda and then with water, to remove acid compounds, and then distilled at reduced pressure to remove light ends.  Instead of refluxing the mixture of azelaic acid, polyethylene glycol and C8 oxo alcohol, a half ester may first be prepared by refluxing a mixture of the azelaic acid and polyethylene glycol, in the presence of toluene and sodium bisulphate, until no further formation of water occurs. The C8 oxo alcohol may then be added and the mixture again refluxed until no further formation of water occurs.  The finished product contains about 30-35 volume per cent diester and 65-70 volume per cent complex ester.  The phenothiazine may be prepared by heating diphenylamine and sulphur in the presence of iodine.  The crude product may be purified by precipitating the phenothiazine from a solution in acetone by the addition of water.ALSO:Non-corrosive lubricating compositions, suitable for use in turbo-jet and turbo-prop aircraft engines, comprise a blend of 20-95 per cent by volume of a C6-C16 branched chain alcohol diester of a dicarboxylic acid with 80-5 per cent by volume of a complex ester as defined below, 0.1-5 per cent by weight of phenothiazine and 0.1-5 per cent by weight of a condensation product of an aromatic aldehyde with a diamine, the percentages by weight being based on the total composition.  The diester may be derived from C6, C7, C8 or C9 oxo alcohols and oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic or sebacic acids.  The complex ester has one of the following formulae:- (I) <FORM:0774457/III/1> wherein R1 and R5 are the alkyl radicals of monocarboxylic acids, R2 and R4 are glycol residues, R3 is the alkylene radicle of a dicarboxylic acid and x is a whole number, (II) <FORM:0774457/III/2> wherein R1 and R5 are the combining radicles of the alcohols R1 OH and R5OH, R2 and R4 are the alkylene radicles of a dicarboxylic acid, R3 is a glycol residue and x is a whole number and (III) <FORM:0774457/III/3> wherein R1 is the alkyl radicle of a monohydric alcohol, R2 is the alkylene radicle of a dicarboxylic acid, R3 is a glycol residue, R4 is the alkyl radicle of a monocarboxylic acid and x is a whole number.  Monohydric alcohols suitable for use in preparing the complex esters include alkanols, oleyl alcohol and ether alcohols formed by the reaction of ethylene oxide or propylene oxide with aliphatic alcohols, while suitable glycols include those containing ether oxygen atoms and/or thioether sulphur atoms, particularly polyethylene glycols.  Additional ingredients which may be present in the lubricating compositions are amines (e.g. primary, secondary and tertiary alkylamines, such as bis-2 - ethyl hexyl amine( bis (di - 2 - ethylhexylamino) methane, C6-C24 primary amine mixtures, trihexylamine and octadecylamine), tricresyl phosphate, other oxidation inhibitors (e.g. polynuclear phenols and alkylated phenols), detergents (e.g. petroleum sulphonic acids and their metal salts), rust inhibitors (e.g. polyhydroxy esters such as sorbitan mono-oleate and penta-erythritol mono-oleate), lecithin, foam suppressants (e.g. silicones) and mineral oil.  In an example, a lubricating composition consists of a diester (derived from C8 oxo alcohol and azelaic acid), a complex ester (derived from azelaic acid, polyethylene glycol having a molecular weight of about 200, and C8 oxo alcohol), purified or commercial phenothiazine and an ethylene diaminesalicylaldehyde condensation product.  For comparison purposes, similar compositions are described in which either the phenothiazine or the amine-aldehyde condensation product is omitted.  Also for comparison purposes, compositions are described consisting of a diester (derived from 2 - ethyl hexanol and sebacic acid), a complex ester derived from sebacic acid, polyethylene glycol having a molecular weight of about 200 and 2 - ethyl hexanol), tricresyl phosphate and either (a) purified phenothiazine or (b) commercial phenothiazine together with one of di - 2 - ethylhexyl amine, bis (di - 2 - ethylhexyl amino) methane and a mixture of C12-C16 aliphatic primary amines.